docs: def _update_progress_bar(self):
          # type: (Downloader) -> None
          """Update progress bar
          :param Downloader self: this
          """
          blobxfer.operations.progress.update_progress_bar(
              self._general_options,
              'download',
              self._download_start_time,
              self._download_total,
              self._download_sofar,
              self._download_bytes_total,
              self._download_bytes_sofar,
          )